Investigation Of Shale Gas Turbulent Premixed Flame Using Direct Numerical Simulation

Environmental pollution and energy shortage are important factors that restrict the development of human society,so it is urgent to seek new fuels and high efficient,clean combustion equipment.As an unconventional natural gas,shale gas has many advantages such as large reserves,less pollutant emissions from combusting and so on.Its reasonable mining and utilization are important to the optimization of energy structure and environment protection in China.The deep understanding of the characteristics of the reactive flow in shale gas combustion process is the basis for the design and manufacture of efficient and clean combustion equipment.Based on the reduced shale gas chemical reaction mechanism constructed in this thesis,the direct numerical simulation of turbulent premixed shale gas flame is conducted to study the interaction between turbulence and flame in shale gas combustion process comprehensively,and the influence of stretching and bending on the flame characteristics is discussed.The main work and results of this thesis are as follows:(1)In order to obtain more efficient,accurate reduced mechanism,a new mechanism reduction approach based on multistage sensitivity analysis is proposed.The validation of various conditions and fuels proves its high efficiency and practicability.Based on this approach,the skeleton reaction mechanism of shale gas with 26 species and 44 reactions was constructed,which is essential in the simulation of combustion process.(2)In order to obtain the detailed characteristics of the interaction between combustion and flow,based on the basic conservation rule of combustion process,a parallel direct numerical simulation system for turbulence combustion simulation is constructed.The typical turbulent combustion results of several fuels demonstrate the availability of the direct numerical simulation code.The construction of the simulation analysis platform provides a powerful analytical tool for the detailed simulation of the shale gas combustion process.(3)Combined with the chemical reaction mechanism of shale gas,three-dimensional direct numerical simulation of shale gas turbulent premixed flame was carried out by using the direct numerical simulation system constructed in this thesis.The interaction between turbulence and flame was analyzed through the shale gas turbulent premixed combustion process,and the influence of jet velocity,equivalence ratio and other initial parameters on the flame characteristics was obtained.The work of this thesis is helpful to the deep understanding of shale gas combustion characteristics,thus providing guidance for the design of reasonable and efficient shale gas combustion equipment and providing theoretical basis for further exploitation and utilization of shale gas.The mechanism reduction approach and the direct numerical simulation method proposed in this thesis provide a new idea for the analysis of complex reaction flow.